The present invention relates to belt sanders and particularly to belt sanders which are adapted to be used in wood working operations.
Many wood working projects call for odd shapes of wood to be cut out. Such pieces of wood often have compound curves, inside and outside radii and transitions between lines and curves. Such shapes are often necessary to the function, or are to add a decorative touch to the project.
After cutting a board into the approximate desired shape, a woodworker must sand the board to final shape and finish. The faces of the pieces are readily sandable with many sanding devices on the market. The bigger problem lies in sanding the edges.
Drum type sanders do a good job at sanding without much effort. Their principal drawback however is that a woodworker must maintain an inventory of various size drums and sand paper sleeves for each drum size. The sand paper sleeves are expensive and wear out quickly. A further hindrance is that when the drum sizes are changed, the tool or motor which drives the sanding drum may not be able to vary its speed (r.p.m.) easily or accurately if at all. This is important because the quality and ease of sanding is dependent upon the surface feet per minute at which the sand paper contacts the work piece.
Belt sanders do well on straight edges and on larger outside curves. Most belt sanders present the sanding belt on a vertical plane perpendicular to the face of the board. The sanding belt passes over a flat surface in the area where the grit contacts the workpiece. This arrangement makes it difficult to sand inside a concave radius. The following U.S. Patents illustrate some of the belt sanders and grinding tools known in the art.
U.S. Pat. No 2,538,044 to Ruehle illustrates a belt sander attachment for a power tool. The attachment has a spindle adapted to be inserted in and gripped by a chuck. The spindle fits within a sanding belt head drum. A set screw is used to insure that the spindle and head drum rotate together. The attachment further comprises an adjustable tail drum assembly. The axes of the drum heads may be changed to adjust for uneven belts.
U.S. Pat. No. 2,640,303 to Johnson exemplifies an endless belt knife sharpening and grinding attachment. The grinder has vertically disposed pulleys with a belt having a grinding outer surface trained over the pulleys. The pulleys are rotated by a motor carried by the base. Tension in the grinding belt is maintained by a spring member.
U.S. Pat. No. 2,857,717 to Edgemond, Jr. et al. illustrates a belt sander having a base and a frame assembly for supporting a pair of pulleys over which a sanding belt is positioned. The frame assembly is pivotally mounted on the frame for movement between a number of positions. The sander further includes a table assembly which moves relative to the belt and which can act either as a fence or a table.
U.S. Pat. No. 4,201,254 to Fehric relates to a woodworking structure capable of performing a number of different operations such as cutting and grinding. The structure includes a pivotable motor and pulley attachments for accommodating an endless grinding or sanding belt. The pulley attachments include belt support members attached to the work table. The support members and the belt are driven by the motor and a pair of pulleys attached to the motor and one of the support members.
U.S. Pat. Nos. 4,578,906 to Appleton and 3,713,255 to Welsch illustrate hand-held grinding tools. In the Appleton tool, the idler pulley may be replaced only by replacing the entire arm assembly. In the Welsch tool, the support assembly may be disassembled to replace the pulley.
U.S. Pat. No. 4,443,977 to Gaiani illustrates a grinding tool for machining skew surfaces. The tool has a series of adjustable shaping rollers to machine the skew surface. The position of each roller is controlled individually to form the desired curved configuration.
One of the problems associated with belt sanders is that a woodworker is limited by the diameter of the pulley under the sanding belt. Additionally, most belt sanders present the belt vertically making it very difficult to hold and maneuver the workpiece.
Accordingly, it is a principal object of the present invention to provide an improved belt sander that enables a woodworker to form wood articles having compound curves, inside and outside radii, and transitions between lines and curves.
It is a further object of the present invention to provide a belt sander as above having a number of different diameter pulleys which can be quickly replaced without the use of tools.
It is yet a further object of the present invention to provide a belt sander as above having an adjustable work table to bevel an edge, chamfer or add a decorative edge.
It is still a further object of the present invention to provide a belt sander having improved belt tracking.
Still further objects and advantages will become more apparent from the following descriptions and drawings wherein like reference numerals depict like elements.